Figure 1.
Monthly variations of dry weather flow at the Vidy Bay WTP inlet.
Flow is normalized to the annual mean flow, which is m3. The monthly baseflow fluctuates between +40/−25% of the mean.
Figure 2.
Schematic view of the Vidy Bay WTP basin considered in this study.
The main pipes of the collection system are illustrated with bold lines. Hospitals and clinics for acute somatic treatment are located using grey pentagons. The total number of hospital beds in the basin is about 1600, which corresponds to a total of approximately 8 beds per 1000 inhabitant.
Figure 3.
Annual antibiotics sales estimated for the city of Lausanne.
Blue: ambulatory sales, red: total sales. From one year to the next, the contribution of hospitals to the total load of antibiotics consumed varies little. Likewise, ambulatory sales show little variation.
Table 1.
Description of the antibiotics sales datasets.
Table 2.
Excretion ratio (in % of amount consumed) in urine for the different substances investigated.
Figure 4.
Seasonal fluctuations of antibiotic sales are shown in the left column.
ambulatory (dark grey, left axis) and hospitals (light grey, right axis). The data are normalized to the annual mean. On the right side of the figure, two columns of plots show periodograms for ambulatory sales and hospital usage (left to right, respectively). The peak in the ambulatory-sales periodogram occurs at 0.08 month−1, i.e., a period of 12 months for these sales, indicated by the dashes.
Figure 5.
Ratio of hospital use to total use for the Lausanne WTP basin.
Results are presented for clindamycin (green), trimethoprim (red) and ciprofloxacin (blue). This ratio shows considerable volatility, depending on the month and substance considered.
Table 3.
Correlation coefficient of ambulatory and hospitals sales.
Table 4.
Minimum/Mean/Maximum ratio (in %) of antibiotics originating from hospitals found Lausanne wastewater, calculated from 5 years of monthly consumption data.
Figure 6.
Computed monthly PEC at WTP inlet (one box per month).
Each box was obtained from five monthly total sales data (total of 5 y of data available, giving 5 sets of each month). The red line locates the median of the five months considered. Upper and lower box limits correspond to the and
percentiles, respectively. Upper and lower whiskers correspond to the last datum being within 1.5IQR of the higher and lower quartile, respectively. IQR is the interquartile range, i.e., the difference between the upper and lower quartiles.